Water sources for automotive electrolyzers

ABSTRACT

The present invention provides a self-replenishing liquid water source onboard an automobile for supplying liquid water to an electrolyzer, such as an on-board hydrogen generator useful for the suppression of unwanted emissions. While automobiles typically have water reservoirs resupplied by a person, the invention provides a passive means of water collection for reliable replenishment due to operations of the automobile itself. The invention provides condensate from the engine exhaust gas by cooling a region of the exhaust system using cooling fluid from the engine coolant system. The cooling fluid is circulated during a period following the engine cold start event when the heat load on the engine coolant system is low.

This is a continuation-in-part application of application Ser. No.08/991,085 filed on Dec. 16, 1997 abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of providing water for useon-board an automobile. More particularly, the present invention relatesto operating an electrolyzer on-board an automobile.

2. Background of the Related Art

Catalytic converters are commonly used to reduce unwanted emissionsthrough catalytic combination of the emissions with oxygen from the air.Catalytic combination, often referred to as catalytic combustion, is aflameless process in which mixtures of emissions (or fuel) and air (oroxygen) are passed over a catalyst at a temperature high enough to favortotal oxidation of the emissions (or of the fuel). The reaction occursat the catalyst surface resulting in liberation of energy and productionof reaction products. For organic fuels, the reaction products areprimarily carbon dioxide and water.

The control and suppression of unwanted emissions created by theoperation of an internal combustion engine is a primary considerationfor engine designers and vehicle manufacturers because of nearlyworld-wide governmental requirements regarding acceptable emissionlevels. Over eighty percent (80%) of the unacceptable emissions orpollutants created by internal combustion engines equipped withcatalytic converters occur during cold start operations. Thesepollutants are emitted for a period of one to three minutes after coldengine starting, in large part because that is the time period requiredfor the catalyst to reach an efficient operating temperature. Therefore,even though the engine exhaust is flowing through the catalyticconverter, until the exhaust heats the catalytic converter to itsoperating range from engine start up, the engine emissions are onlyslightly catalytically decomposed during that time period.

In order to meet governmental emission standards for internal combustionengine exhaust, a catalytic converter is located in the exhaust streamof the engine. The converter typically includes a canister holding asuitable catalyst, such as a three-way catalytic converter (TWC)catalyst monolith, that will oxygenate unburned, unacceptable componentsin the exhaust stream including hydrocarbons (HC), their partiallyoxidized derivatives such as aldehydes and carbon monoxide (CO), and atthe same time reduce nitrogen oxides (NO_(x)), after almoststoichiometric fuel bum with oxygen in the cylinders of the engine. Theexhaust gas is passed through the catalyst monolith, thereby completingthe oxygenation of unburned HC and CO, and the reduction of NO_(x) inthe exhaust to convert these unacceptable emissions into acceptableemissions. Certain unacceptable emissions in the exhaust stream,including unburned hydrocarbons and carbon monoxide, require anoxidation reaction to destroy them so that they end up as thecorresponding oxides, e.g., water and carbon dioxide. On the other hand,NO_(x) requires a reduction reaction to develop N₂ and O₂. In fact, theO₂ product of this reduction contributes to the oxidation of the HC andCO in the exhaust.

Catalytic converters are typically manufactured by coating a substrate,such as a metal or ceramic material, with a high surface area material,typically a metal oxide media. The catalytic material, such as a noblemetal, is then deposited on the high surface area material. In theformation of such a catalytic converter, a sintered, dense and hardenedceramic substrate for example, which can be in the shape of a honeycomb,wagon-wheel, spiral or other molded or shaped objects, or simply be inthe form of pellets, is coated with a slurry of the high surface areamaterial, after which the catalyst is applied to the slurry-coatedsubstrate, typically by application of a solution of a salt of thatmetal.

More particularly, the underlying ceramic substrate can be cordierite,mullite, alumina, lithium aluminosilicates, titania, zircon, feldspar,quartz, fused silica, clays, kaolin clay, aluminum titanate solidsolutions, silicates, zirconia, spinels, glasses, glass ceramics,aluminates, and mixture thereof The constituent ceramic materials aregenerally admixed with binders or shaping agents, processed, moldedwhere applicable, and sintered. Coating of the substrate with the highsurface area media can be effected either by immersion or dipping,followed by heat-treating the coated substrate at a temperature between500° C. and 600° C. Procedures for depositing a high surface area“wash-coat” on the previously sintered ceramic substrate are disclosed,for example, in U.S. Pat. No. 3,824,196. Following application of theslurry of high surface area material, the catalyst is applied in themanner stated above. Alternatively, a single “wash-coat” mixture of thehigh surface area media and the catalytic material can be appliedtogether.

TWC catalysts are currently formulated and designed to be effective overa specific operating range of both lean and rich fuel/air conditions anda specific operating temperature range. These particular catalystcompositions enable optimization of the conversion of HC, CO, andNO_(x). This purification of the exhaust stream by the catalyticconverter is dependent on the temperature of the exhaust gas and thecatalytic converter works optimally at an elevated temperature,generally at or above about 300° C. “Light-off temperature” is generallydefined as the temperature at which fifty percent (50%) of the emissionsfrom the engine are being converted as they pass through the catalyst.The time period between “cold start” and reaching the light offtemperature is generally referred to as the “light-off time.”

The conventional method of heating the catalytic converter is to heatthe catalyst by contact with high temperature exhaust gases from theengine. This heating, in conjunction with the exothermic nature of theoxidation reaction occurring at the catalyst, will bring the catalyst tolight-off temperature. However, until the light-off temperature isreached, the exhaust gas passes through the catalyst relativelyunchanged. In addition, the composition of the engine exhaust changes asthe engine heats from the cold start temperature, and the catalystmonolith is typically designed to work best with the composition of theexhaust stream produced at the normal elevated engine operatingtemperature.

There have been several attempts to shorten or avoid the light-off timeof the catalytic converter. Current techniques employ one of thefollowing methods: electrical heating of the exhaust gases and/or of thecatalytic converter itself; thermal insulation of the exhaust lineand/or the catalytic converter; multi-chambered configurations of thecatalytic converter; placing the catalytic converter adjacent to theengine for heating; combustion of fuels upstream of the catalyticconverter; and catalytic combination of fuels and oxygen at the catalystsurface. All of these methods have drawbacks and limitations.

Placing the catalytic converter almost immediately adjacent to theengine is not desirable because of the tendency to overheat the catalystwith resulting accelerated degradation of the catalyst. Thermalinsulation is also not a desirable option because of the same problems,especially during operation at maximum operating temperature ranges.

Electrical heating of catalytic converters (“EHC”) has been a popularproposed method of attempting to preheat the catalyst monoliths.Limitations on the equipment and process, however, affect the utility ofthis method. The primary limitation on electrical preheating is theelectrical energy required by the heater. The typical car battery is nota practical power source to supply the electrical power because theelectrical load on the vehicle battery during the period required mayexceed the rated battery output. In any event, the load placed on atypical 12 volt vehicle battery will shorten the lifetime of thebattery. Also, there is a measurable delay between the time the operatorof the vehicle places the ignition switch in the “on” position and thetime the heater brings the catalyst to light-off temperature.

Typically, in the interval between start up and light-off, the exhauststream is oxygen deficient. Because the catalyst requires oxygen tocomplete the catalytic reaction, supplemental air must be blown over thecatalyst. Even when using a secondary air flow to overcome oxygendeficiency, the secondary air flow must be closely controlled to avoidan excess of oxygen, in which case the catalytic converter is lesseffective in reducing NO_(x). However, it should be noted that NO_(x)contributes a very small portion of unacceptable emissions when anengine is cold; most of the cold start emissions that must be dealt withcomprise HC, CO and the like.

An alternative to battery powered electrical heating has been todecrease the strain on the power supply by supplying the power directlyfrom an alternator rather than directly from the vehicle battery. Analternator powered, electrically heated catalyst (“APEHC”) stillrequires a 5 to 10% increase in battery capacity to cope with the EHCstart-up scenario. Even with the APEHC system, there is still a concernwith respect to battery capacity because electrical heating is neededfor an extended period of time, i.e., more than 25-30 seconds. Inaddition, the maximum alternator power output required in the APEHCsystem requires a complicated switching mechanism and an alteredalternator speed between 2,000 and 4,500 rpm during the heating up timeperiod, and the alternator must be oversized.

The multi-chamber configurations of catalytic converters generallyconform to one or two theories. In one multi-chamber configuration, asmall portion of catalyst known as a “starter catalyst” is positionedupstream from the primary catalyst. This “starter catalyst” is generallycloser to the exhaust manifold. This location, in conjunction with asmaller thermal mass associated with its smaller size and materials ofconstruction, causes the catalyst to heat much more quickly than theprimary catalyst. This configuration, however, is generally unacceptablebecause the starter catalyst in the exhaust stream creates a higher backpressure which reduces the overall engine efficiency and robs the engineof power output.

Another method of providing multiple chambers in the exhaust flowincludes a first catalyst having low temperature characteristics usedonly during cold start conditions, and, after the catalyst temperaturerises to a certain elevated level, the exhaust gas flow is switched topass through the conventional catalytic converter configuration. Avariation of this approach is to run all cold start emissions through aseparate absorber (such as a zeolite or a molecular sieve-typesubstance) where unacceptable emissions are captured and later releasedback into the exhaust stream. This method, however, is impracticalbecause of the complicated switching mechanism used to divert flow tothe absorber, the size and space requirements of the absorber, and theimpracticality of releasing the unacceptable emissions from the absorberback into the exhaust stream.

An additional method for reducing cold start emissions runs the engineexcessively rich in the cold start condition and ignite the resultingsuper-rich mixture to directly heat the catalyst. This approach hasproved wholly unreliable and has other serious drawbacks, includingreduced engine and catalyst life.

Catalytic combination of a fuel with oxygen at the surface of thecatalyst generates heat that can rapidly bring the catalytic converterto light off temperature. For example, the introduction of hydrogen to aTWC catalyst can heat portions of the catalyst to 300° C. or greaterwithin a period of several seconds. However, the significant amount ofhydrogen necessary to cause this rapid, high temperature heating makesit impractical to store enough hydrogen for any large number of heatingcycles. Consequently, it is a practical result that hydrogen must begenerated onboard the vehicle.

Hydrogen generation using a proton exchange membrane electrolyzer isdescribed by Appleby in U.S. patent application Ser. No. 08/320,171.Appleby teaches the use of an electrolyzer to convert water to hydrogengas at the cathode. The hydrogen may then be collected and/or dried foruse upon demand. However, the continued operation of the electrolyzer isdependent upon the availability of water to the electrolyzer. While theelectrolyzer may be provided with a refillable water reservoir locatedunder the hood, this setup leaves the emissions control system reliantupon the user to actually maintain the water level.

Benz et al. (U.S. Pat. No. 5,658,449) teaches a method and a device fornitrogen oxide reduction in a vehicle's exhaust gas by its reductionwith hydrogen gas on a catalyst mounted in the exhaust system. Benz etal. proposes two methods of generating the required amount of hydrogen,via electrolysis of water aboard the vehicle, or via chemical productionof hydrogen from a fuel, e.g., methanol, gasoline, or diesel fuel, viathe well-known steam reforming reaction. Benz et al. also teaches that,in association with the former approach, the water required by anelectrolyzer may be recovered from the vehicle's exhaust gas system.While Benz refers more specifically to the operation of a diesel engine,it is well known that today's gasoline engines operate at close tostoichiometric fuel-air levels, i.e., very little free oxygen is presentin the vehicle's exhaust.

A major limitation of the Benz et al approach is the difficulty incondensing water under the conditions desribed. For example, agasoline-type fuel is arbitrarily represented to have a chemicalcomposition corresponding to octane, C₈H₁₈, or in shorthand, CH_(2.25),then 3.125 atoms of oxygen are required for complete combustion of thefuel to give carbon dioxide (CO₂) and water vapor (H₂O). While inpractice combustion is not complete, in a modem engine with emphasis onreduction of exhaust emissions it is very nearly so, so that thisapproximation will serve.

Oxygen (O₂) comprises approximately 21% by volume of dry air, theremainder being the inert gas nitrogen with about 1% argon and otherinert trace gases. Ambient air at 25° C. at 60% of its saturation levelwith water vapor contains 1.88% by volume of water vapor. The amountvaries with temperature and degree of saturation, but it never exceeds6.5% under extreme tropical conditions. Thus, typical 25° C. ambient airhas the composition 20.6% by volume oxygen, 77.5% inert gases, and about1.9% water vapor, which also corresponds to its molecular composition.20.6 molecules (41.2 atoms) of oxygen will combust 13.184 (CH_(2.25))units, giving 13.184 molecules of CO₂ and 14.832 molecules of H₂O. Theexhaust gas will therefore have a rounded composition of 13.2 CO₂, 16.7H₂O, and 77.5 inert gases, giving a total of 107.4 molecules from theoriginal 100 of air. The exhaust gas therefore contains 15.5% by volumeof water vapor. When the engine in the vehicle is operating, the exhaustgas is extremely hot, therefore water recovery will require cooling,since condensation will not start to occur until it is cooled to 55° C.Under extreme tropical conditions, a similar calculation shows that thecorresponding exhaust gas composition contains a total of about 19.3%H₂O, which will require a condensation temperature of less than 59.6° C.The total water requirement for the Benz et al. disclosure under cruiseconditions is 0.035 kg of water per hour, which is continuously removedfrom the exhaust gas produced by the engine. At a probable fuelconsumption of 28 mpg (11.9 km/liter, 17.0 km/kg) under 92.2 km/hr(maximum) FTP cycle conditions, the maximum speed of this cycle, fuelconsumption is about 5.42 kg per hour.

This amount of fuel yields 7.7 kg of water when combusted. Hence, lessthan 0.5% of the water produced need be collected. However, exhaust gasfrom a hot engine is at a high temperature, in excess of 350° C., andmeans must be found to cool about 78.4 kg per hour of exhaust gas fromthis temperature to 55° C. (under the stated 25° C. ambient temperatureconditions) to condense some of the water. Actual condensation of thesmall amount of water required will require the removal of about{fraction (1/1000)} of the heat removed from the hot gas. The latterwill require 25° C. ambient air in a quantity equal to about 10 timesthe weight of the exhaust gas per hour. Under 34.1 km/hr (maximum) FTPcycle conditions, internal combustion engine characteristics are suchthat the fuel consumption (in mpg, km/liter, or km/kg) will not changemuch, so that at the maximum speed of this cycle the fuel consumed isabout 2.0 kg per hour, and the quantities of water vapor and totalexhaust gas produced must be correspondingly less, namely 2.85 and 28.9kg per hour. The quantity of exhaust gas to be handled at a steady 92.2kph is 68,000 liters of exhaust gas per hour (about 19 liters persecond). This must be handled in such a way as to cause no back-pressureon the engine. The necessary exhaust gas-to-air heat exchanger willrequire a very large surface area for effective heat transfer to takeplace. In general, the amount of heat rejected from the engine in theform of hot exhaust gas from an internal combustion engine is as much asthree times the amount rejected from the liquid-cooled radiator. Sincethe exhaust gas-to-air heat exchanger (condenser-radiator) must workunder similar conditions to this radiator (i.e., under all practicaloperating conditions, including idle, and all outdoor temperatures), andwill have a similar heat rejection temperature to air, a very largeradiator will be required. This solution is therefore not practical.

Therefore, there is a need for a reliable water supply for theautomotive electrolyzer. It would be desirable if the water supply werereplenishable without human involvement. It would be even more desirableif the water could be supplied in sufficient quantities to supporthydrogen generation and storage for use during cold starts and/or forcontinuous use combating nitrogen oxide emissions.

SUMMARY OF THE INVENTION

The present invention provides a self-replenishing water source for anelectrolyzer onboard an automobile comprising a condensate collectionreservoir; and a means of transferring the water having an inlet influid communication with the condensate reservoir and an outlet in fluidcommunication with a water reservoir. The condensate collectionreservoir may be located in the muffler or in the tail pipe.Furthermore, the water source may further comprise a filter and either adeionization bed or a distillation apparatus in fluid communicationbetween the condensate reservoir outlet and the water reservoir.

The invention also provides an on-board hydrogen generation system,comprising: a condensate collection reservoir; a conduit providing fluidcommunication between the condensate collection reservoir and an anodewater reservoir; an electrolyzer having an anode in communication withthe anode water reservoir, a cathode, and a proton exchange membranedisposed between the anode and the cathode; and a source of electricalcurrent having a positive terminal coupled to the anode and a negativeterminal coupled to the cathode.

Further, the invention provides a method for providing water to anelectrolyzer on board an automobile comprising the steps of: condensingwater vapor to form a condensate; collecting the condensate; andsupplying the condensate to the electrolyzer. Water vapor may becondensed in some region of the exhaust system using cooling fluid fromthe radiator system. The method may further comprise filtering andpurifying the water and may also further comprise storing the water in awater storage reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the features and advantages of the present invention can beunderstood in detail, a more particular description of the invention,briefly summarized above, may be had by reference to the embodimentsthereof which are illustrated in the appended drawings. It is to benoted, however, that the appended drawings illustrate only typicalembodiments of this invention and are therefore not to be consideredlimiting of its scope, for the invention may admit to other equallyeffective embodiments.

FIG. 1 is a schematic diagram of a hydrogen production and deliverysystem of the present invention for heating a catalytic converter.

FIG. 2 is an exploded view of an electrolyzer suitable for use in thesystem of FIG. 1.

FIG. 3 is a schematic diagram of a water collection system taking watercondensing in the exhaust muffler of an automobile.

FIG. 4 is a schematic diagram of a water collection system taking watercondensing in the exhaust tailpipe of an automobile.

FIGS. 5A and 5B are schematic diagrams of water collection systems thatcondense steam from the radiator of an automobile.

FIG. 6 is a schematic diagram of a water collection system taking waterrunoff from the windshield of an automobile.

FIG. 7 is a schematic diagram of a water collection system condensingwater out of ambient air or cabin air of an automobile.

FIG. 8 is a schematic diagram of a liquid water recovery system thatutilizes cooling fluid from an engine coolant system to condense watervapor from the engine's exhaust gas stream.

FIG. 9 is a schematic diagram of a liquid water recovery system havingan electronic control scheme to limit the heat load of an exhaust gasheat exchanger on the engine coolant system.

FIG. 10 is a schematic diagram of a liquid water recovery system havinga control system that is independent of the engine management system.

FIG. 11 is a schematic diagram of a liquid water recovery system havinga slip stream capable of continuous operation.

FIG. 12 is a schematic diagram of a liquid water recovery system capableof revaporizing the liquid water.

FIG. 13 is a schematic diagram of a water vapor transfer line in thermalcommunication with the exhaust pipe to allow water vapor to be carriedto a point higher in the vehicle than the exhaust system.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method and apparatus for providing asource of water on-board an automobile without requiring intervention byan operator. The source of water may be used in various manners and forvarious purposes, including replenishment of water reservoir levels andconsumption by an on-board electrolyzer for producing hydrogen. Whilethe water source may utilize electrical power from the automobile foroperation, for example to power a pump, the water source may be designedto operate in a completely or mostly passive manner.

In one aspect of the invention, water is obtained by condensing watervapor from various vapor or gas streams available on, in, or to, theautomobile. Water vapor streams that may be condensed include the cabinair, steam from the radiator, ambient air or exhaust gas passing throughthe muffler or tail pipe, and the like. Each of these water vaporstreams presents unique conditions for condensing the water vapor andcollecting the liquid water. Differing process conditions andenvironmental factors affect the reliability, operability and capacityof the various water vapor streams.

In another aspect of the invention, water condensed from the vaporstreams may optionally be passed through a filter, such as a porouscarbon fiber material, porous ceramic, or porous metal, and/or adeionization resin bed to remove undesirable particulates, contaminantsand salts. Optionally, the system for providing water may include apump, capillary action, or gravity flow to transfer the water from thecondensing surface through the filter and resin bed or directly to awater reservoir.

In yet another aspect of the invention, water condensed in accordancewith the invention is prevented from freezing. Optionally, the water maybe transferred or maintained in thermal communication with a componentof the automobile that is warm during operation, for example the exhaustsystem or engine. Furthermore, the water may be optionally collectedthrough a conduit that will empty when water collection is completed. Ineach or a combination of these configurations, the water may beprevented from forming ice within the conduit and possibly causingdamage to the system or failure of the water collection system.

In a further aspect of the invention, systems may optionally be providedto cause or enhance the condensation of the water vapor. Condensationmay be caused using cooling coils such as those in an air conditioningunit, thermoelectric devices in combination with or independent of anyair conditioning unit, steam condensing coils having forced aircirculation therearound and the like.

In yet a further aspect of the invention, the water sources of thepresent invention may be provided at ambient pressure or at elevatedpressure, such as by a water pump, an electrolytic pump or by directcommunication with the pressurized steam from the radiator.

Preferably, the water source is of suitable quantity and quality to beused in the electrolytic production of hydrogen. The catalytic converterof the automobile may be chemically heated by feeding hydrogen to thecatalyst along with some air or oxygen. It is desirable to heat thecatalyst in order to enhance the conversion of unacceptable emissionsemanating from an internal combustion engine into water and otheracceptable emissions. In one aspect of the invention, hydrogen gas issupplied from an electrolyzer or other hydrogen source and injected intothe monolith of a catalytic converter to more rapidly bring the catalystto a light-off temperature. Heating or thermally conditioning a catalystin accordance with the invention rapidly brings the catalyst up to thelight off temperature for the efficient conversion of pollutant gases,such as unacceptable emissions emanating from an internal combustionengine, into water, carbon dioxide and other acceptable emissions.

FIG. 1 shows a system 10 of the present invention installed on a vehicleexhaust system. The vehicle includes a catalytic converter 12 located inan exhaust line 14 from the exhaust manifold of a vehicle's engine 16.The exhaust line 14 is provided with air from an air pump 18 andhydrogen from a hydrogen inlet line 20. The air pump 18 could be anysuitable air source, such as a blower, for injecting air into theexhaust line 14 at suitable pressure and volumetric flow rate to achievea suitable or ideal air/hydrogen ratio mixture.

The hydrogen supply system of the invention generally includes a waterreservoir 22, an electrolyzer 24, and a hydrogen storage cylinder 26. Asshown in FIG. 1, the electrolyzer 24 may preferably compromise aplurality of stacked identical cells 28. The reservoir 22 serves both asa water reservoir and as a separator for oxygen and water. The reservoir22 may be a vehicle's windshield washer fluid storage container, but ispreferably a dedicated reservoir allowing separation of oxygen from thewater withdrawn from port 34. Water flows by gravity drain or is pumpedfrom the reservoir 22 to the electrolyzer 24 via a drain line 30. As theelectrolyzer produces hydrogen and oxygen, the oxygen and entrainedwater flows naturally back to the reservoir 22 via a return line 32.

The next major component of the hydrogen source is the electrolyzer 24,shown in greater detail in FIG. 2. In the following description of theelectrolyzer 24, the materials of construction referred to as“preferred” are the material actually used in a test device to provethat the invention would work for its intended purpose. In commercialproduction models of the present invention, where possible, lessexpensive materials may be used throughout, such as carbon steel fortitanium where possible, and plastic such as polypropylene where heatand stress will permit the use of such material.

The electrolyzer 24 may be referred to herein as a proton exchangemembrane (PEM) electrolyzer. The proton exchange membrane 40 itself mayprove corrosive in this environment in contact with certain substances,thus requiring the careful selection of the material of construction ofthe electrolyzer. For example, the PEM 40 will preferably only contactcarbon or graphite. However, those of skill in the art will readilyrecognize that materials less exotic than those listed in the followingdiscussion can be readily employed without penalty for components thatare located away from the PEM material itself and the oxygen electrodecatalyst. For example, graphite will be the material of choice incertain structural elements, and not some obvious candidates such ascopper, aluminum, or iron, which can corrode thus forming ions that canpoison the oxygen and/or hydrogen electrode catalysts.

In FIG. 2, the PEM electrolyzer 24 is shown as a cell stack including apair of endplates 36 and 38. The endplates 36 and 38 are preferablytitanium. Adjacent the top endplate 36 is an anodic cell frame 42. Thecell frame 42 is preferably a carbon fiber-filled Teflon sheet, soldunder the trademark Zymaxx by Du Pont. The cell frame 42 retains a 1:1molar ratio of iridium and ruthenium dioxides (IrO₂/RuO₂) as the anodicelectrocatalyst. The cell frame 42 also includes a plurality of flowports 44 to permit the supply of reactant (water) and/or removal ofelectrolysis product (oxygen gas). An expanded titanium metal currentcollector (flow field) 46, preferably 25 Ti 40-3/32 from Exmet Corp. andan anode substrate 48, preferably a porous titanium plate measuringabout 0.05 inch thick, are disposed within the cell frame 42. Adjacentthe anode substrate 48 is the proton exchange membrane 40, preferablycut from a sheet of perfluoronated sulfonic acid polymer, such as NAFION117 available from Du Pont of Wilmington, Del., which serves as a solidelectrolyte material and is preferably about 175 μm thick.

FIG. 2 depicts a gasket 50, one of perhaps several installed whererequired. Gaskets 50 are preferably stamped from 0.033 inch thickfluorosilicone sheet (Viton) and from 0.005 inch thick unsintered PTFEsheet. The electrolyzer 24 further includes a cathodic gas diffusioncathode 52 and an expanded titanium flow field 54.

Finally, the PEM electrolyzer 24 includes a cathodic cell frame 56,preferably made of polychlorotrifluorethylene (PCTFE) sheet, sold underthe trademark KEL-F by Afton Plastics. The cathodic cell frame 56retains flow field 54 and the gas diffusion cathode 52.

As shown in FIG. 2, the various components of the PEM electrolyzer arestacked together and retained with a plurality of tie rods 58,preferably 16 such tie rods. Stainless steel tubing, such as SS316, arethen screwed into four threaded ports on one of the titanium endplates.The ports typically include a water inlet port 60, the oxygen outletport 62, and a pair of hydrogen outlet ports 64. To minimize electricalcontact resistance, the titanium endplates 36 and 38, as well as theexpanded titanium metal current collectors 46 and 54, may beelectroplated with a thin film of gold or other noble metals, such asplatinum.

The cathode and the anode of the electrolyzer are of specialconstruction. The cathodic electrode structure for hydrogen evolution isfashioned from a commercially available fuel cell gas diffusion layer ona carbon cloth backing, which acts as a support for the activehydrophilic electrocatalyst layer. This active layer contains highsurface area colloidal platinum (100/m²/g), supported on carbon black(60 wt % Pt on C), yielding a platinum loading of 4.0 mg/cm². Thecathodic electrode structure, having an area of 40 cm², was hot-pressedonto one side of a segment of precleaned NAFION 117 PEM material.Hot-pressing was carried out between the plates of a hot-press elevatedto 200° C. for 60 seconds using a force of about 15,000 pounds.

For the anodic electrocatalyst layer, a 1:1 molar ratio of iridium andruthenium chlorides are dissolved in ca. 8 ml of concentrated HCl andheated to almost dryness. The resulting chlorides are then dissolved inisopropanol to make an ink-like coating. A porous titanium plate, 0.05inch in thickness from Astro Met of Cincinnati, Ohio, is etched in 12%HBF₄ for 60 seconds and rinsed with isopropanol. This substrate is thencoated with the ink-like mixture and the solvent evaporated under lowheat of about 90° C. This coating and drying procedure may be repeatedany number of times, preferably several times and most preferably seventimes, before the electrode is heated in a furnace at 400° C. for 10minutes in ambient air. The coating, drying, and furnace treatment isrepeated twice more, but with a final baking time of two hours insteadof 10 minutes.

Referring back to FIG. 1, the system further includes a hydrogen storagecylinder 26 and various supporting components in addition to thereservoir 22 and the electrolyzer 24, described above. The supportingcomponents optionally include a liquid water trap 70 to eliminate mostof the entrained water from the hydrogen exiting the electrolyzer, asolenoid valve 72 to blow out the trap, a check valve 74, and a pressurerelief valve 76 to protect the system against over pressurization.

As previously described, the electrolyzer 24 includes a proton exchangemembrane in its construction so that generated oxygen is vented to thewater reservoir 22 and the hydrogen generated can be accumulated atpressure. Prior to operation, the system permits purging of the hydrogenhandling system with an inert gas, such as nitrogen, to remove all airfrom the system downstream of the check valve 74. Furthermore, thecontrol of hydrogen to the catalyst in the catalytic converter mayoptionally be managed by a controller and solenoid valve. Theintroduction of hydrogen may be initiated by a switch, such as theautomobile's ignition switch or a dedicated preheat switch, and stoppedupon reaching a given temperature within the catalyst.

FIG. 3 is a schematic diagram of a system 80 for collecting condensatefrom the muffler 82 in the exhaust line 14 of an automobile's engine 16.Warm water vapor in the exhaust gases may condense in contact with thecooler surfaces of the muffler 82, particularly when the engine is firststarted or in idle and the muffler is presumably at or near ambienttemperatures. In accordance with the invention, the muffler is providedwith a collection reservoir or pan 84 that allows the condensate toaccumulate. A small pipe or other channel 86 is provided incommunication with the reservoir 84 from either above or below thereservoir 84 in order to withdraw the water as it accumulates. The pipe86 is shown here having a terminal end extending into the reservoir 84,but maintaining a gap 88 between the terminal end and the wall of thereservoir 84. When the reservoir is filled, a suction pump 90 draws thewater up the pipe 86 and through a filter 92, cation/anion exchangeresin bed 94 and into the water reservoir 22. The pump 90 is preferablycapable of running dry and self-priming. Optionally, the system 80 maybe run only during periods when the muffler is expected to be cool, suchas during engine startup or when the car is idling.

FIG. 4 is a schematic diagram of a system 100 for collecting condensatefrom the exhaust tailpipe 102 of an automobile. The preferred locationfor collecting tailpipe condensate is near the terminal end of thetailpipe, since this location is the farthest from the engine (coolest)and condensate may even be collected from the ambient air, presumablybecause the reciprocating action of the engine causes air to be pulledinto the tailpipe as well as exhausting gases. It is preferred that thetailpipe 102 includes a screen 108 to resist entry of dust, dirt andother foreign matter from entering the tailpipe 102.

In order to enhance condensation in the tailpipe, the terminal six totwelve inches or so of the tailpipe may optionally include one or morecooling fins around the exterior of the pipe. The flow of air passingover the tailpipe as the automobile travels will cool the tailpipe.

A water collection reservoir 104 is located along the bottom surface ofthe tailpipe 102 to capture or collect condensate. While the water maybe withdrawn from above (as with pipe 86 of FIG. 3), the water is shownhere being withdrawn through a drain tube 106 in fluid communicationwith the reservoir 104. The remainder of the water collection system 100operates in a fashion similar to system 80 of FIG. 3.

FIG. 5A is a schematic diagram of a water collection system 110 thatcondenses steam from the radiator 112 of an automobile. A typicalradiator system 112 will have a radiator cap 113 with a pressure reliefset at about 12 psig. The system 110 communicates steam from theradiator through a steam line 114 and check valve 116 to a waterreservoir 118 which operates above atmospheric pressure, but preferablyno greater pressure than about 15-20 psig or thereabout. When thereservoir pressure is less than the radiator pressure, steam flows intothe reservoir. Once the reservoir and radiator pressures roughlyequilibrate or the pressure differential is insufficient to keep thecheck valve 116 open, then the check valve 116 closes. As the steamwithin the reservoir 118 condenses, the pressure in the reservoir drops.After the reservoir pressure drops a sufficient amount, the check valvewill reopen to refill the reservoir with steam. Because the electrolyzeroxygen output line 32 is returned to the reservoir 118, the oxygen beinggenerated by the electrolyzer will eventually increase the pressure inthe reservoir and stop the passage of steam into the reservoir from theradiator. When the pressure in the reservoir gets too high, the solenoidvalve 122 will open and release the oxygen, lower the reservoir pressureand allow additional steam to enter the reservoir. In this manner, thepressure in the reservoir 118 is controlled by a pressure relief valve120 and a solenoid release valve 122 or, possibly, a controlled leak.This cycle continues to provide water to the reservoir 118 withoutreliance on operator attention.

The system will preferably include a filter 124 in the steam line 114 toprevent passage of particulates. Furthermore, because the water iscollected by condensing steam, the water is substantially free ofinorganic salts. Any traces of anti-freeze in the condensate prevents orat least suppresses freezing in the water reservoir.

FIG. 5B is a schematic diagram of an alternate water collection system130 that condenses steam from the radiator 112 of an automobile as itpasses through the inside of a coil 132 that is cooled by passing air,presumably air rushing past as a result of the automobile's speed orradiator cooling fan. The condensate is collected into a reservoir 134.Should the reservoir 134 over fill, steam or condensate may pass throughthe conduit 136 back into the radiator 112 or to the cooling waterreservoir. Condensate from the reservoir 134 may optionally be passedthrough a deionization bed 138 before being passed to the waterreservoir 140 having a pressure relief valve 142 thereon. It should berecognized that the water collection system 130 operates at a pressurehigher than that of the radiator, for example about 12 psig, higher thanthe radiator pressure.

FIG. 6 is a schematic diagram of a water collection system 150 takingwater runoff from the windshield 152 of an automobile. While rainwatercould be collected at various locations on an automobile, the frontwindshield 152 is preferred because there is already a built-in channel154 for drainage of the water away from the windshield and because thewindshield receives water not only during rainfall, but also duringwindshield cleaning and car washing.

FIG. 7 is a schematic diagram of a water collection system 160condensing water out of ambient air or cabin air of an automobile.Conventional air conditioning systems include a fan 162 and a coolingcoil 164 containing a refrigerant. As humid air passes over the coolingcoil 164, water vapor may condense out of the air. In accordance withthe present invention, a collection reservoir 166 is portioned below thecoil 164 to catch the condensate as it drips off the coil. Thecondensate may then pass to the water reservoir 22 by gravity drain orby using pump 90. Preferably, the system will also include a filter 92and resin bed 94. While this system is dependent upon the automobile infact having an air conditioner installed, the same or similar resultscan be achieved by a dedicated system, perhaps based on the use of athermoelectric cooling device or combination of devices to condensewater vapor.

A preferred method of obtaining water from the exhaust gas produced bythe engine involves condensing water from the exhaust gas only during acold start of the engine. Alternatively, water condensing may beperformed whenever (a) there is a need for more water, and (b) a watercondensing portion of the exhaust gas system is at a temperature at orbelow that necessary to condense water from the exhaust gas. Morespecifically, the water is preferably condensed by a condenser that isheat exchanged with cooling fluid from the radiator system over a periodof time following engine startup but before the maximum heat rejectionload of the radiator is reached.

Water condensing may be achieved using a small heat exchanger or devicewhich is in thermal communication with the exhaust gas system. The heatexchanger or device is preferably located downstream of the catalyticconverter, e.g., either between the catalytic converter and muffler, ordownstream from the muffler, to avoid heating the heat exchanger ordevice by hydrogen used in heating the catalytic converter on coldstarting the engine. The heat exchanger or device preferably containssuitable metal winglets extending into the exhaust gas stream to createturbulence and to aid in heat transfer, which will also help preventfouling, and may also include external fins for heat dissipation.

It is also preferred that the heat exchanger or device in the exhaustsystem be cooled by a fluid circulated through tubes from the engine'sradiator cooling circuit. In this device, the fluid may be passedthrough a conduit having any of a variety of thermal relationships withthe exhaust gas stream or exhaust gas system, including a conduitdisposed within or around the exhaust gas conduit itself. Even at highambient temperatures (40° C.), such a heat exchanger or device couldcondense 50% of the water out of the exhaust gas during the first fiveminutes after an engine cold start. Optionally, the flow of coolingfluid from the radiator could be automatically shut-off followingcondensation of an amount of water. It is also optional that thecondensed water may be automatically transferred to a separate waterstorage reservoir.

Under 40° C. ambient conditions, it is estimated that 119 g of watercould be condensed out of the exhaust gas from an engine producing 2.85kg water vapor per hour, and 321 g of water could be condensed out ofthe exhaust gas from an engine producing 7.7 kg water vapor per hour,for an average of 220 g water per cold startup. This amount of water issufficient to supply hydrogen for several hours for nitrogen oxidecontrol (average 24 g per hour) by the method of Benz et al., andsufficient to heat up the catalytic converter for several cold starts,since it has been determined that 25 liters of hydrogen, correspondingto about 18 g of water consumed in the electrolyzer, are sufficient forthis purpose. The water supply may also be supplemented, as necessary,by pure water condensate from the vehicle's air-conditioning heatexchanger. Under cold-weather conditions, this will not be available,but the engine cold start time will be longer, allowing for the recoveryof more water from the exhaust gas produced by the engine.

FIG. 8 is one embodiment of a liquid water recovery system that utilizescooling fluid from the radiator attached to the engine of a vehicle tocondense water vapor from the engine's exhaust gas stream. In thisembodiment, the engine 301 has a liquid-to-air heat exchanger orradiator 302 to reject heat produced in the engine to the ambient. Whenthe engine of the vehicle has not been operated for some time, thetemperature of the entire engine and exhaust gas system 300 may be nearambient temperature. Under this condition, after the engine is started,cool liquid from the radiator 302 is generally prevented from flowingthrough the engine until the engine has reached a suitable operatingtemperature. During this warm-up period, the cooling liquid iscirculated between the radiator and the exhaust gas system to condensewater from the exhaust gas through the use of a liquid-to-gas heatexchanger 304 and water collection system 309 placed after the catalyticconverter 303 and before the muffler 305. Alternatively, the heatexchanger and water collection system may be placed after the muffler305 but before the tail pipe 306. Water collected in the condensatecollection system 309 may be transferred through a fluid conduit 310 toa water pretreatment system 311 before storage in a water reservoir 312.The water pretreatment system 311 may include particulate filteringelements, activated carbon filters and mixed resin bed deionizationcartridges.

FIG. 9 shows one embodiment of an electronic control scheme to limit theheat load of the exhaust gas heat exchanger 304 on the engine coolingsystem. The cooling system includes a radiator 302, water circulationpump 313, and the engine water cooling system 314. In this embodiment,the engine management system 315 monitors many system parameters such asthe temperature of the engine or cooling system 316. This enginetemperature may be used to change the position of a valve 317 whichallows or prevents cooling fluid from circulating between the radiator302 and the exhaust gas heat exchanger 304. In one possible controlscenario, cooling fluid from the radiator 302 is allowed to flow throughthe exhaust gas heat exchanger 304 where it serves to cool the hotexhaust gas 318 from the engine resulting in water being condensed fromthe cool exhaust gas 319 in either the heat exchanger 304 or in a followon condenser. When the engine reaches the desired operating temperaturethe control valve 317 may be closed to remove the heat load of the heatexchanger 304 from the radiator 302. In another scenario, or possiblyunder extreme conditions, the exhaust gas water condenser system may beallowed to operate until the radiator has reached its maximum heatrejection capabilities and the valve 317 must then be closed to preventthe engine cooling system from being overloaded giving rise to anoverheated engine. In some circumstances, it may be desirable to utilizethe heat in the hot exhaust stream to reduce the warmup time of a coldengine. In this mode of operation, the control system may allow thecirculation of cooling fluid between the exhaust heat exchanger untilthe engine has reached a desired temperature.

FIG. 10 shows an alternate embodiment of a control system which does notrely on the engine management system for control. A thermostaticexpansion valve 322 may be placed in a primary coolant conduit 320 or321 leading to, or away from, the engine cooling system 314respectively. The closing temperature of this thermostatic element canbe selected such that cooling fluid flow to the exhaust gas heatexchanger through coolant line 307 is directly controlled by thetemperature of the coolant. In this manner, surplus heat removalcapacity of the radiator may be automatically utilized by the exhaustgas heat exchanger and condenser system and waste heat from the exhaustsystem may be used to warm the engine without an external controlsystem.

FIG. 11 is an embodiment of the engine exhaust water vapor condensationsystem which provides a continuous mode of operation. It is recognizedthat only a small portion of the water vapor in the exhaust gas streamis required for any process which may consume water on-board a vehicle.Actively cooling all of the exhaust gas from an engine is impracticaldue to the quantity of the exhaust gas and velocity of the exhaust gasthrough the exhaust system. In this continuously operating system,exhaust gas from the engine 301 passes through the appropriate aftertreatment system 303, such as a catalytic converter, and is divided intotwo streams with the primary exhaust gas stream continuing through themuffler 305 and tail pipe 306. At some point in the exhaust system, aportion of the exhaust gas is separated using a flow divider 323 whichallows a fraction of the exhaust gas to flow through a conduit 328 at amuch reduced velocity. This slip stream of exhaust gas is then cooled asit travels through the length of the conduit, represented as 324, or byutilizing finned heat exchangers 325 or a liquid cooled heat exchanger331 or any combination of condensers. Condensed water is collected in acollection subsystem 326 before the exhaust gas is rejoined with theprimary exhaust gas stream at 327. Through design of the size, length,and flow resistance of the primary exhaust stream 329, 305, 330 and thelow-flow slip stream 328, 324, 325, 331, 326, 327, the degree of coolingof the exhaust gas slip stream and subsequent condensation of water fromthe exhaust gas can be engineered.

FIG. 12 is one embodiment of an engine exhaust water recovery system 340that operates only once per vehicle start. This embodiment condenseswater from the engine exhaust gas stream while the engine and exhaustsystem are cold and subsequently utilizes the hot exhaust system toevaporate and purify the condensate. In this embodiment, the primaryexhaust pipe 332 is fitted with a member 333 to reduce the velocity ofthe portion of the exhaust gas nearest the sidewalls to prevent thecondensed water from being carried completely out of the exhaust systemby the high exhaust gas flow velocity. This condensate is allowed to runinto a collection reservoir 334, 335 through a conduit 336. While notshown in this embodiment, the system may also be fitted with ambientcoolers or liquid cooled heat exchangers as described previously. Wateraccumulation takes place so that a significant portion of the liquidwater that normally drips from the tail pipe of a cold exhaust system isrecovered into the reservoir 334, 335.

Furthermore, the recovered liquid water is distilled in the recoverysystem when the primary exhaust pipe gets hot after extended engineoperation, thereby providing a first stage of water purification. Duringoperation of the engine, the exhaust pipe 332 will reach normaloperating temperature and the system may be designed such that thehousing of the reservoir 334 approaches or exceeds the boilingtemperature of water and the water within the reservoir 334 isevaporated. This water vapor may leave the reservoir 334 through adischarge port 337 and associated conduit 338. Since the conduit 338contains primarily water vapor, the water vapor is readily condensedsince the heat load of the exhaust has been eliminated from thecondensing system. This condensed water is collected in a reservoir 339and transferred by a lift pump 343 to its ultimate storage reservoir. Ifdesired, the water reservoir 334 may be designed with a well 335 that isthermally isolated such that it remains near ambient temperature,preventing the evaporation of all the water in the well and forming awater seal around conduit 336. This prevents exhaust gas from passingthrough the condenser 338 and into the reservoir 339. Alternatively, asmall and well controlled vent 341 may be provided to allow a controlledamount of exhaust gas to be cooled in the condenser 338 and aid in themovement of water vapor from the reservoir 334, through the condenser338 and into the water reservoir 339.

In an alternate embodiment as shown in FIG. 13, the placement of thecondenser 338 and the degree of thermal contact between the exhaust pipe332 and the water vapor transfer line 342 allows water vapor to becarried to a point higher in the vehicle than the exhaust system. Inthis manner, water vapor may be delivered to the engine compartmentwhere it may be condensed and stored at a point above that at which itis consumed. This method of water condensate recovery may be designed tooperate in a completely passive manner since it would eliminate thewater transfer pump necessary to lift the condensate from a sump underthe vehicle to a reservoir in the engine compartment.

It should be recognized that the condenser described above could be usedto provide water for any one or more applications on present or futureautomobiles that rely upon a source of water. Specifically, the watercould supply one or more electrolyzers and the windshield wiperreservoir.

While the foregoing is directed to the preferred embodiment of thepresent invention, other and further embodiments of the invention may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims which follow.

What is claimed is:
 1. A method for supplying liquid water to anelectrolyzer onboard an automobile having an engine and an engineexhaust gas system comprising the steps of: (a) cooling a condensingregion of the exhaust gas system; (b) passing exhaust gas from theengine through the condensing region, wherein the exhaust gas containswater vapor; (c) transferring heat from the exhaust gas to thecondensing region; (d) condensing the water vapor from the exhaust gasin the condensing region to form liquid water; and (e) delivering theliquid water to the device.
 2. The method of claim 1, further comprisingthe step of: (f) filtering and purifying the liquid water.
 3. The methodof claim 1, wherein the step of condensing water vapor is performedduring a cold start event of the engine.
 4. The method of claim 3,wherein the automobile further comprises an engine coolant system, andfurther comprising determining the beginning of the cold start event ofthe engine by satisfying one or more engine ignition initiatingconditions selected from the group consisting of: (i) the cooling fluidtemperature in the engine coolant system is below a temperaturesetpoint; (ii) the amount of time elapsed since the engine waspreviously operated exceeds a time setpoint; (iii) the temperaturedifference between the exhaust gas and the radiator cooling fluidexceeds a differential temperature setpoint; (iv) the engine blocktemperature is below a temperature setpoint; and (v) combinationsthereof.
 5. The method of claim 3, wherein the automobile furthercomprises an engine coolant system, and further comprising determiningthe ending of the cold start event of the engine by satisfying one ormore stop conditions selected from the group consisting of: (i) thecooling fluid temperature in the engine coolant system exceeds atemperature setpoint; (ii) the amount of time elapsed since thebeginning of the cold start event exceeds a time setpoint; (iii) thetemperature difference between the exhaust gas and the cooling fluid inthe engine coolant system is less than a differential temperaturesetpoint; (iv) a reservoir receiving the liquid water is full; (v) theengine block temperature exceeds a temperature setpoint; and (v)combinations thereof.
 6. The method of claim 1, wherein the condensingregion is a conduit supplied with a slip stream of exhaust gas inparallel fluid communication with the exhaust gas system.
 7. The methodof claim 6, wherein the step of cooling is performed continuously. 8.The method of claim 6, wherein the conduit has a diameter less than halfthe diameter of the exhaust pipe.
 9. The method of claim 6, wherein theconduit has external cooling fins.
 10. The method of claim 6, whereinthe conduit is in thermal communication with cooling fluid circulatedfrom an engine coolant system.
 11. The method of claim 6, furthercomprising: circulating cooling fluid from the engine coolant systeminto thermal communication with the conduit during a period followingthe cold start event of the engine.
 12. The method of claim 1, whereinthe device includes a reservoir.
 13. The method of claim 1, wherein thedevice is an electrolyzer, windshield washer fluid reservoir, orcombinations thereof.
 14. The method of claim 1, further comprising:communicating the liquid water away from the exhaust gas stream; heatingthe liquid water to form a water vapor stream; and recondensing thewater vapor stream to form liquid water.
 15. The method of claim 14,wherein the recondensed liquid water is substantially free ofnonvolatile contaminants.
 16. The method of claim 14, wherein the liquidwater is recondensed at an elevated position within the vehicle.
 17. Themethod of claim 16, further comprising gravity feeding the recondensedliquid water to the device.
 18. The method of claim 6, wherein theautomobile further comprises an air conditioning system having a coolingcoil in thermal communication with the slip stream.
 19. The method ofclaim 1, wherein the condensing region has a gas flow velocity reducingmember.
 20. The method of claim 6, wherein the condensing region of theconduit is elevated above the device.
 21. The method of claim 4, furthercomprising a cooling fluid flow loop from the engine coolant systemhaving a flow control valve that opens at the beginning of the coldstart event.
 22. The method of claim 5, further comprising a coolingfluid flow loop from the engine coolant system having a flow controlvalve that closes at the end of the cold start event.
 23. The method ofclaim 21, wherein the flow control valve is a thermostatic expansionvalve.
 24. The method of claim 22, wherein the flow control valve is athermostatic expansion valve.
 25. A method for supplying liquid water toan electrolyzer onboard an automobile having an air conditioning coolingcoil, comprising the steps of: (a) passing air containing water vaporinto thermal communication with the cooling coil; (b) condensing thewater vapor from the air on the cooling coil to form liquid water; and(c) delivering the liquid water to the device.
 26. The method of claim25, wherein the air is provided by a source selected from the groupconsisting of the automobile cabin compartment, the engine compartment,and combinations thereof.